BioE 411 and AE/CE/BRT 511 Wastewater treatment

Attached growth systems: sewage farms

Morestead sewage farm

Berlin sewage farm layout

Sewage farm

Overland flow designs

Improved attached growth: early biobed

Large-scale wastewater treatment

Rotating disc arrangement

Simple treatment: septic tank

Leach field after septic tank

Suspended growth systems So far, we have studied systems where treatment is effected by bacteria, and other organisms, which are attached to a solid medium, i.e. soil, rocks, etc. There are also systems where the microbial growth occurs in suspension. The bacteria then aggregate into flocs, which are barely visible to the naked eye, but each consists of millions of bacteria and often protozoa attached to the floc. Systems range from the simple facultative lagoon or pond, with no aeration, to aerated ponds and to sophisticated activated sludge systems, where the biomass is separated from the effluent and recycled to treatment and excess production treated separately. The simple lagoon or pond systems purify the water quite well, but since there is no provision to separate the biomass production, the effluent is quite turbid and still contains much organic material, but stabilized to a non-smelling and not rapidly degrading form.

Facultative lagoons Facultative lagoons or stabilization ponds use only natural phenomena and almost no mechanical action. Oxygenation for bacterial oxidation of organics comes from photosynthesis by algae and a bit from wind. CO2 released by bacteria is used by the algae. Excess biomass and other settleables are treated by anaerobic bacteria at the bottom.

Facultative lagoon interactions http://www2.bren.ucsb.edu/~keller/courses/esm223/esm223_15.pdf

Design approaches to pond treatment systems Ponds usually require lengthy treatment periods, weeks for facultative systems and days for aerated systems. Although facultative systems have very little mixing other than inflow, gas bubbles and wind effects, the long retention periods ensures some homogeneity except with respect to depth, as there is much stratification. As in any mixed system, the contents have the same concentration as the overflow. This means that the organisms in the pond continuously experience a low level of substrate to feed on, which slows down the treatment considerably, as the typical first-order reactions are directly proportional to the BOD. Therefore, significant improvement in treatment rate can be achieved by approaching a channel (tube) flow, or using multiple ponds. Multiple pond system analysis can be performed by assuming that each is a completely mixed system, operating on a first-order degradation and a mass balance around each provides one equation. Intermediate values can be eliminated as of no interest, so the solution will provide final effluent quality for given retention times, or more importantly, retention times to achieve a necessary effluent quality.

Activated sludge process

Activated sludge flocs Note filamentous bacteria Note Vorticella and other protozoa

Activated sludge model

Activated sludge plants Hyperion, Playa del Rey, CA)

Primary aeration tank

Oxygenated systems Cryogenic air separation facility, Hyperion, Playa del Rey, CA)

Settling tanks Secondary settling tank, Hyperion, Playa del Rey, CA)

Aerobic suspended systems – activated sludge Volumetric loading = QL0/V QL0

Nitrogen removal Nitrification (Nitrosomonas and Nitrobacter) NH3 + O2  NO2-  NO3- Denitrification NO3- + organics  CO2 + N2 Process adaptations Air Anoxic Aerobic

Phosphate removal BNR plants Discarding phosphate anaerobically Luxury aerobic uptake of P in aerobic stage Process adaptations for N and P removal Air Wastewater Anaerobic Anoxic Aerobic

Excess biomass disposal Production Separation Further biological treatment – (an)aerobic Dewatering Drying – solar or gas heated Disposal/ beneficial use – soil amender/fertilizer or fuel The cost of biomass disposal amount to about half the cost of wastewater treatment. Aeration, if used, almost up to half of the rest of the cost. If no aeration, the capital cost , including the cost of land, could be very high.

Typical steps in modern wastewater treatment

How are living beings classified? Historic development of classification Linnaeus (1735) 2 kingdoms Haeckel (1866) 3 kingdoms Chatton (1925) 2 groups Copeland (1938) 4 kingdoms Whittaker (1969) 5 kingdoms Woese (1977,1990) 3 domains Animalia Eukaryote Eukarya Vegetabilia Plantae Protoctista Fungi Protista (not treated) Procaryote Monera Archaea Bacteria

How are living beings classified? Two super- .kingdoms Three domains Six kingdoms Mineralia non-life Biota/ Vitae life Acytota / Aphanobionta (Viruses, Viroids, Prions?, ...) non-cellular life Cytota cellular life Prokaryota / Procarya (Monera) Bacteria Eubacteria Archaea Archaebacteria Eukaryota / Eucarya Protista Fungi Plantae Animalia

Carl Woese’s Tree of Life